Phonetic sound recognizer

ABSTRACT

Identification of complex signals such as a phonetic sound in speech is accomplished by the combination of ratio values both between the amplitudes and frequencies of the resonances in the complex sound wave. The amplitude ratio between the signals detected from two resonances (e.g. formants) is derived as a null signal when they match a pair of signal-gain preadjustments during a given time period. This null-signal is also obtained when both input signals are absent during that time period. In order to avoid false null-signal indication, a sensing signal is derived from said input signals to indicate that the null-signal is not false.

' United States Patent 1191 Kalfaian 5] Nov. 11, 1975 PHONETIC SOUNDRECOGNIZER Primary E.\'um1'11e/'William C. Cooper [76] Inventor: MeguerV. Kalfaian, 962 Hyperion Assistant L.\lIHll1l--E. S. Kemen.

Ave. Los Angeles, Calif. 90029 57 ABSTRACT [22] Filed: Jan. 3. 1975 1ldent1ficat1on of complex slgnals such as a phonetic PP N01 6 sound inspeech is accomplished by the combination of ratio values both betweenthe amplitudes and fre- [52] CI. 179/1SA quencies of the resonances inthe complex sound [51] Int CL "CIOL 1/00 Wave. The amplitude ratiobetween the signals de [58] Field of Search H SA 1 SC tected from tworesonances (e.g. formants) is derived as a null signal when they match apair of signal-gain [56] References Cited preadjustments during a giventime period. This nullsignal is also obtained when both input signalsare ab- UNITED STATES PATENTS sent during that time period. In order toavoid false 33 3/1969 Kalfflflm 179/1 5A null-signal indication. asensing signal is derived from fi i f f said input signals to indicatethat the null-signal is not 2! a1a1'1..... 3.870.817 Kalfaian 179/1 SA 4Claims, 1 Drawing Figure CHANNEL SWITCHING 11:5[1 PULSE DISTRIBUNR 4RECOGNITMN OUT [4.

SENSE AHPLIF If R TIIRESHIJLD ADI.

U.S. Patent Nov. 11, 1975 PHONETIC SOUND RECOGNIZER This inventionrelates to speech sound wave analysis, and more particularly to theprovision of control signals for indicating the true or false nature ofthe final signal derived as a representation of the desiredphoneticinformation.

In my previous patent disclosures, for example, US. Pat. No. 3,432,617issued Mar. 11, 1969, l have described that the phonetic information, asspoken by different speakers, is represented by the combination of boththe frequency and amplitude ratios between the resonances of a selectgroup of resonances in the complex sound wave. In that patentdisclosure, 1 had described a null indicating circuit with prefixed gainadjustments, so that when two signals having predetermined amplituderatio between the two arrive simultaneously at the inputs of thiscircuit within a given analytical time period, a null output will beobtained as an indication of the phonetic information desired. In suchan arrangement, however, said null output will also be obtained duringsaid time period when both of the input signals to the circuit areabsent, resulting false indication of the desired phonetic information.In order to avoid such false indication, a sensing means is included inthe complete phonetic information analyzing system, as disclosed herein,so as to allow production of the final information representing signalonly when said input signals are present. This will be described in moredetail in the following specification, when read in connection with theaccompanying drawing.

In order to understand the purpose and usefulness of the presentinvention in a system of speech sound recognition, the drawing consistsof a complete system of phonetic sound recognition, wherein, the voicesound wave in block 1 is first amplitude equalized in block 2, andapplied to a set of band-pass filters in blocks 3 through 6. Thesefilters are used to sub-divide the frequency spectrum of speech soundwaves, and the outputs of these band-pass filters are detected in blocks7 through 10, respectively. The outputs of these detectors are thenanalyzed for deriving the desired information as representation of aphonetic sound in the spoken sound wave.

Due to the enormous amount of spectral variations that occur in normalspeech sound waves, I have described in my patent issue No. 3,622,706issued Nov. 23, 1971, a system of spectral normalization by waynumerical identity conversion in a special arrangement of numericallyidentified switchable channels. I have also described a simplified andmore practical arrangement of the switchable channels in my patentapplication Ser. No. 368, 265 filed July 8, 1973, now US. Pat. No.3,864,518, issued Feb. 4, 1975, which is included in the presentdisclosure representing the channels 1 through n, in the accompanyingdrawing. These channels are numerically identified, and each oneconsists of a number of channel-switching AND-gates depending upon thenumerical location in the numerical sequence, for example, the channel-1consists of the largest number of AND-gates; the channel-2 consists ofone less than that number; the channel-3 consists of one less than thenumber of AND-gates in the preceding channel; and so on. These AND-gatesare represented by the channelswitching transistors Q1 through Q10,which admit input signal to output only when simultaneous inputswitching signal is present. Thus, the drawing shows that the outputs ofblocks 7 through 10 are applied to one of the input electrodes of Q1,Q5, Q8, Q10, respectively, the outputs of which are connected inparallel to the input of output-transistor Q11, which allows admit tanceof any one of the output signals of detector blocks 7 through 10 to theinput of output-transistor 011 by applying switching pulse to the otherinput electrodes of the gate-transistors by the pulse distributor inblock 11. Besides such multiple switching of selected input (detected)signal to the channels, for ex- I ample, channel-l, the switching inputelectrodes of these AND-gates are connected in parallel in an order,such that when the second (numerically identified) input signal isswitched to the input of the first channel, the third input signal isswitched to the input of the second channel, as represented by thetransistor Q12, and by the parallel connections of the signal-inputelectrodes of the AND-gates, for example, Q5-Q2; Q8-O6- Q3; andQl0-Q9-Q7-Q4. Such an arrangement facilitates shifting of the inputsignal to the channels in such numerical order that, the signal havingthe lowest numerical identity at the outputs of the detectors in blocks7 through 10 is shifted to the first channel, with proportionalnumerical shifting of the other signals to respective channels. Thischannel-identity numerical conversion is important for final analysis ofthe information to be derived from the detected signals. For example, ifthe numerical ratios between the numerically identified group ofdetected signals represent the information desired, this group of signalmay arrive at the detectors such that the signal having the lowestnumerical identity may arrive at any one of the detector blocks 7through 10, because of spectral variation in the voice sound spectrumfrom block- 1. Whereas, by channel identity shifting, such that thesignal having the lowest numerical identity is shifted to the output ofthe first channel, the selection of these signals from standardnumerical locations from the channel outputs becomes much simpler forfinal analysis by matching with standard parameters. Such simplenumerical channel switching, however, also requires sub-division ofresonances in the sound spectrum by the band-pass filters in an order ofharmonically increasing series of frequencies, and said seriescomprising a plurality of subseries, all sub-series having the samenumber frequencies such that each frequency in a sub-series isharmonically related to the same-placed frequency in the othersub-series. These band-pass filters are then numbered sequentially fornumerical identity in the same numerical sequence of the channels, asshown in the drawing, so as to make the channel identity shifting of thenumerically identified detected signals without destroying theiroriginal numerical ratio identities. This has been more fully explainedand illustrated in my reference patent application, now patentNo.3,864,518, issued Feb. 4, 1975. By such spectral normalization, in themode of channel identity shifting, any group of signals that may beselected from the outputs of the band-pass filters in blocks 3 to 6,will be shifted to a standard numerical location at the outputs of thechannels, and thereby, selection of the important output signals fromthe outputtransistors Q11 to Q14 will be standardized for simpleanalysis. This is simply accomplished by the pulse distributor in block11, which activates the switching inputs the said AND-gates sequentiallyuntil one of the switching operations position a desired group ofsignals from the outputs of the detectors 7-10 in the correct numericallocation at the outputs of the channels.

After spectral normalization has been established, the final step ofinformation analysis is the measurement of the amplitude ratios betweenthe selected signals. This is done, for example, by measuring the signalamplitude ratio between the output signals of the output-transistors Q11and Q12, from across output resistors R9 and R10. With the assumptionthat the signal amplitude ration is consistent for a particularinformation, for example phonetic sound, then we may make fixedtap-adjustments across these resistors, so that the signal amplitudesacross these resistors will be equalized whenever this particularinformation arrives. Recognition of the equalized state of two signalsbecomes simple by null-signal identification, as in the following:

With the above given explanation, assume now that the signals at thetaps across output resistors R9 and R10 are of equal amplitudes asrepresentation of a particular information, during a pulse period fromthe distributor in block 11. These equalized signals are applied to theinputs of an operational amplifier in block 12, which by virtue of itsinvert and non-invert inputs, the net output will be zero (null) signal,or at least below a threshold minimum amlitude level; this zero outputrepresenting the desired information. The output of block 12 is appliedto an amplifier in block 13, which converts the single-ended input intoa push-pull output. This push-pull output is then further applied to asense amplifier in block 14, which produces an output signal of prefixedpolarity, regardless of the polarity of the arriving signal at itspush-pull input. The purpose of such an arrangement is that, when theinput signals of block 12 are of different amplitudes, representingfalse information, the single ended output of block 12 may be in eitherpositive or negative polarity, depending on which of the two inputsignals is larger than the other. Since commercially available senseamplifier integrated circuits are usually provided with double-endedinputs, the amplifier in block 13 is used for the required signalpolarity conversion. The sense amplifier in block 14 is usually providedwith a threshold level adjustment, and it can be manually adjusted to afixed level, so that the sense amplifier in block 14 will produce anoutput signal only when its input signals are above a fixed thresholdamplitude level.

With the functional operations of the amplifiers in blocks 12, 13 and14, as described above, the output of sense amplifier in block 14 willbe in quiescent state when the input signals of block 12 are of equalamplitudes, and in ON-state when the input signals of block 12 are indifferent amplitudes. Assuming thus, that when the arriving signals atthe inputs of operational amplifier in block 12 are of equal amplitudes,and the output of sense amplifier in block 14 is at 0 level during adistribution pulse period, both the distribution pulse and the outputsense amplifier are applied at 0 levels to the AND-gate in block 15,which in turn produces an output pulse at 1 level. This output pulse ofI level may then represent the information desired, and may be utilizedin any desired mode, for example, for the operation of a key of atypewriter. In the case that the input signals of the amplifier in block12 are of different amplitudes during the pulse period of thedistributor in block 11, then the output of sense amplifier in block 14will be in ON-state (1 level), and the 0 level distribution pulseapplied to the AND-gate in block 15 will not operate, thus avoidingfalse signal output from the gate circuit. The signal amplitudebalancing is shown between only two signals, but of course, more thattwo signals can be balanced within the pulse period of the distributor,such as described and illustrated in my related patent application Ser.No. 368,264 filed June 8, 1973 now U.S. Pat. No. 3,864,518, issued Feb.4, 1975, the illustration of which is only exemplary, and commerciallyavailable integrated devices suitable for the purpose may be used.

With the above given explanation, it will be noted that the presence ofthe desired information is determined by the OFF-state of the senseamplifier in block 14. This OFF-state will also prevail when the inputsignals to the operational amplifier in block 12 are both absent duringa distribution pulse period. In order to avoid such false indication ofinformation, each pair of signals at the channel outputs is firstchecked to make sure that one or both of the signals are present. Thisis easily accomplished by applying the output of the first channel (fromthe source circuit resistor R5) to one of the inputs of the inputs ofthe sense amplifier in block 17. With the presence of signal at itsinput, the sense amplifier 17 will produce an output pulse by theoneshot that it may contain, as available commercially. The operatingtime of this one-shot may be adjusted to be equal to the pulse timeperiod of the distribution pulse from block 11, so that during adistribution pulse the sense amplifier will simultaneously produce asimilar output pulse at 0 level when an input signal is present at theinput of channel-l. This pulse from the output of sense amplifier inblock 17 is simultaneously applied to the three-input gate in block 15,so that only when the three inputs of the gate are simultaneously at 0level will cause operation of the gate, as a representation of theinformation desired, thus making sure that false indication ofinformation is not performed. The distributor in block 11 may be freerunning ring distributor, or it may be reset after an informationsignals has been derived, by applying the output of gate 15 to the mixerin block 16, and further applying it to the resent input of thedistributor, as shown.

Having described the preferred embodiments of the invention disclosedherein, and in view of the broad scope of uses it may embrace inpractice, it is obvious to the skilled in the art that it may beconsidered as exemplary, and therefore, various modifications,adaptations, and substitutions of parts may be made without departingfrom the true spirit and scope of the invention.

What I claim, is:

l. A signal matching system for deriving an information-representingsignal from the signal-amplitude-ratio between first and second signalswhen said ratio matches with an arrangement of prefixedsignalamplitude-ratio adjustments in first and second channels during apredetermined time period in which a control signal is produced, saidsystem comprising means for producing said control signal; first andsecond channels; coupling means from said first and second signals tosaid first and second channels, said channels having prefixedsignalamplitude-gain adjustments, so that the signal-amplitudes of saidfirst and second signals are equalized at the outputs of said first andsecond channels in the form of a null signal only when thesignal-amplitude-ratio between said first and second signals matcheswith said prefixed adjustments; a signal sensing means for deriving asensing signal from said first and second signals; and means forderiving a discrete signal representing said information from the cludedmeans for translating said null-signal. said control-signal, and saidsensing signal into similar-polarity signals; a multi-input gate; andmeans for applying said similar-polarity signals to the inputs said gatefor ob- .taining said discrete signal.

4. The system as set forth in claim 1, wherein is included couplingmeans from said discrete signal to said means for producing saidcontrol-signal for resetting them to normal states after said discretesignal is used.

1. A signal matching system for deriving an informationrepresentingsignal from the signal-amplitude-ratio between first and second signalswhen said ratio matches with an arrangement of prefixedsignal-amplitude-ratio adjustments in first and second channels during apredetermined time period in which a control signal is produced, saidsystem comprising means for producing said control signal; first andsecond channels; coupling means from said first and second signals tosaid first and second channels, said channels having prefixedsignal-amplitude-gain adjustments, so that the signal-amplitudes of saidfirst and second signals are equalized at the outputs of said first andsecond channels in the form of a null signal only when thesignal-amplitude-ratio between said first and second signals matcheswith said prefixed adjustments; a signal sensing means for deriving asensing signal from said first and second signals; and means forderiving a discrete signal representing said information from thecombination of said null-signal, said control-signal, and saidsensing-signal, last said signal making sure that said null-signal isderived only from the presence of said first and second signals, and notfrom their absence in said channels.
 2. The system as set forth in claim1, wherein said first and second channels consist of an operationalamplifier for producing said nulL-signal at its output.
 3. The system asset forth in claim 1, wherein is included means for translating saidnull-signal, said control-signal, and said sensing signal intosimilar-polarity signals; a multi-input gate; and means for applyingsaid similar-polarity signals to the inputs said gate for obtaining saiddiscrete signal.
 4. The system as set forth in claim 1, wherein isincluded coupling means from said discrete signal to said means forproducing said control-signal for resetting them to normal states aftersaid discrete signal is used.